Diaphragm pump

ABSTRACT

A diaphragm pump is provided. The diaphragm pump comprises a housing that comprises a concave portion, a suction port and a discharge port; a diaphragm; a first and second pump chamber; and a suction-side check valve and a discharge-side check valve. The suction-side and discharge-side check valves are more distant from the diaphragm in the inner end side of the suction and discharge ports and are closer to the diaphragm in the outer end side of the suction and discharge ports.

This application claims the benefit of Japanese Patent Application No. 2005-258898 filed Sep. 7, 2005, which is hereby incorporated by reference.

BACKGROUND

1. Field

A diaphragm pump with a slim variable volume chamber is provided.

2. Related Art

A diaphragm pump, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 2001-193656, is constructed with pump chambers (variable volume chambers). The pump chambers are defined by a diaphragm and a pair of check valves having different flow directions that are provided in a pair of channels connected to the pump chamber (a suction-side check valve that allows a flow toward the pump chamber and a discharge-side check valve that allows a flow from the pump chamber are provided in the two channels). The suction-side check valve opens at a stroke for increasing the volume of the pump chamber by oscillating the diaphragm and the discharge-side check valve opens at a stroke for decreasing the volume of the pump chamber to operate the pump. The diaphragm is made of an elastic (oscillatable) material, for example, a rubber, or a piezoelectric oscillator.

The diaphragm pump enables a variable volume chamber to be slimmer and includes a diaphragm. The diaphragm pump is used as a slim pump, for example, a cooling water circulation pump of a water-cooled notebook computer.

There is a need, however, for a diaphragm pump that is slimmer.

SUMMARY

A diaphragm pump is provided that comprises pump chambers that are partitioned by a concave portion formed in a housing and an oscillating diaphragm that obturates the concave portion. A suction port and a discharge port are formed in the housing in a direction along with a plain of the diaphragm and of which inner ends communicate with the pump chamber. A suction-side check valve is provided between the inner end of the suction port and the pump chamber. A discharge-side check valve is provided between the inner end of the discharge port and the pump chamber. With respect to a plane, which is perpendicular to the diaphragm and contains an axis line of the suction port and a plane that is perpendicular to the diaphragm and contains an axis line of the discharge port, the suction-side and discharge-side check valves are slanted so that they are more distant from the diaphragm in the inner end side of the suction and discharge ports and are closer to the diaphragm in the outer end side of the suction and discharge ports.

The axis lines of the suction and discharge ports can be formed in parallel with an extending plane of the diaphragm. It is preferable that the axis lines of the suction and discharge ports are not in parallel with the extending plane of the diaphragm and is slanted with respect to the extending plane of the diaphragm so that an angle between the extending plane of the diaphragm and a plane where the suction-side and discharge-side check valves provided is less that an angle between the axis lines of the suction and discharge ports and the extending plane of the diaphragm.

It is desirable that the suction-side check valve and the discharge-side check valve are formed as suction-side and discharge side check valve units that are separate from the housing. The suction-side and discharge-side check valve units are attached to pump chamber side opening ends of the suction and discharge ports. It is also possible that the suction-side and discharge-side check valve units are provided on the same substrate.

It is desirable that the check valve has an umbrella shape. In addition, it is practical that the diaphragm is constructed with a piezoelectric oscillator or an electrostriction oscillator. Specifically, it is desirable that the diaphragm is a bimorph type piezoelectric oscillator.

In the preferred embodiments, the diaphragm pump can be slimed down by improving location relation between the suction and discharge ports and the suction-side and discharge-side check valves that are formed in the pump chamber-side inner ends of the suction and discharge ports that are gateways.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an exploded perspective view of an exemplary diaphragm pump according to a preferred embodiment.

FIG. 2 is an exploded cross sectional view of the exemplary diaphragm pump shown FIG. 1.

FIG. 3 is a top plan view of an exemplary lower housing.

FIG. 4 is a cross sectional view taken along the line IV-IV of FIG. 3.

FIG. 5 is a cross sectional view taken along the line V-V of FIG. 3.

FIG. 6 is a top plan view of an exemplary pump chamber plate side of an upper housing.

FIG. 7 is a top plan view of an exemplary pump chamber that comprises a concave portion of a pump chamber plate.

FIG. 8 is an exploded perspective view of an exemplary bimorph type piezoelectric oscillator.

FIG. 9 is a perspective view that illustrates a relation between the exemplary bimorph type piezoelectric oscillator and a deformed D shape seal ring.

FIG. 10 is a top plan view of the same substantial part of FIG. 9.

FIG. 11 is a conceptual view of a four-valve diaphragm pump according to a preferred embodiment.

FIG. 12 is a cross sectional view that illustrates another preferred embodiment, in correspondence with FIG. 4.

FIG. 13 is a cross sectional view, in correspondence with FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An operating mechanism of a four-valve diaphragm pump will be described with reference to FIG. 11. The diaphragm pump includes an upper housing 10, a lower housing 20, a piezoelectric oscillator (diaphragm) 30, and four umbrellas (check valves) 11, 12, 21, and 22. A pump chamber (variable volume chamber) 13 is located between the upper housing 10 and the piezoelectric oscillator 30. A pump chamber (variable volume chamber) 23 is located between the low housing 20 and the piezoelectric oscillator 30. A single port 31 communicates with the suction-side channels 14H and 24H. The suction-side channel 14H communicates with the pump chamber 13 through the suction-side umbrella 11. The suction-side channel 24H is connected to the pump chamber 23 through the suction-side umbrella 22. A single discharge port 32 is connected to discharge-side channels 15D and 25D. The discharge-side channel 15D is connected to the pump chamber 13 through a discharge-side umbrella 12. The discharge-side channel 25D is connected to the pump chamber 23 through a discharge-side umbrella 22.

In the four-valve diaphragm pump, when the piezoelectric oscillator 30 is elastically deformed (oscillates) in forward and backward directions, a volume of one pump chamber 13 or 23 increases and a volume of the other pump chamber 23 or 13 decreases. A stroke for increasing the volume of the pump chamber 13 is a stroke for decreasing the volume of the pump chamber 23. Since the volume of the pump chamber 13 increases, the suction-side umbrella (suction-side check valve) 11 opens to introduce a fluid into the pump chamber 13 from the pump port 31, and since the volume of the pump chamber 23 decreases, a fluid in the pump chamber 23 opens the discharge-side umbrella (discharge-side check valve) 22 to discharge the fluid to the discharge port 32.

A stroke for decreasing the volume of the pump chamber 13 is a stroke for increasing the volume of the pump chamber 23. Since the volume of the pump chamber 23 increases, the suction-side umbrella (suction-side check valve) 21 opens to introduce a fluid into the pump chamber 23 from the suction port 31, and since the volume of the pump chamber 13 decreases, a fluid in the pump chamber 13 opens the discharge-side umbrella (discharge-side check valve) 12 to discharge the fluid to the discharge port 32 The pulsation period at the discharge port 32 can be shortened (the pulsation period is a half of the period in the case where the pump chamber is formed on only one side which is an upper or lower side of the piezoelectric oscillator 30).

A preferred embodiment will be described in reference to FIGS. 1 to 7. The diaphragm pump includes the upper housing 10, the lower housing 20, the piezoelectric oscillator (diaphragm) 30, and a pump chamber plate 40 and has a flattened rectangular shape. The upper housing 10, the lower housing 20, and the pump chamber plate 40 include moldings of resin materials.

The lower housing 20 is the largest molding of the aforementioned moldings. The lower housing 20 is a complex flattened rectangular shape. In the lower housing 20, an opened pump chamber forming concave portion 20 a is formed in the opposing plane of the piezoelectric oscillator 30. The suction port 31 and the discharge port 32 protrude in parallel with each other and are integrated with one of the four side faces of the lower housing 20 (refer to FIGS. 1 to 5).

In the lower housing 20, the suction-side channel 24H is in communication with the suction port 31 and the discharge-side channel 25D that communicates with the discharge port 32 are formed. Channel expanding portions 24Ha and 25Da connected to the pump chamber forming concave portion 20 a are formed at the inner ends of the suction-side channel 24H and the discharge-side channel 25D. Valve retainer concave portions 24Hb and 25Db are formed at ends of the channel expanding portions 24Ha and 25Da close to the pump chamber forming concave portion 20 a.

A suction-side umbrella unit (suction-side check valve unit) 21U and a discharge-side umbrella unit (discharge-side check valve unit) 22U are adhered and fixed to the valve retainer concave portions 24Hb and 25Db. The suction-side umbrella unit 21U and the discharge-side umbrella unit 22U are the same in the structure, except the attachment direction. An umbrella attaching hole 21 c (umbrella attaching hole 22 c) is formed on the center portion of the unit plate 21 a (unit plate 22 a) of which circumference is used as an adhesion portion 21 b (adhesion portion 22 b) with the valve retainer concave portion 24Hb (valve retainer concave portion 25Db). A plurality of channel holes 21 d (channel holes 22 d) are formed on the circumference of the umbrella attaching hole 21 c (umbrella attaching hole 22 c) An umbrella portion 21 g (umbrella portion 22 g) of an umbrella 21 f (umbrella 22 f) in which a central axis 21 e (central axis 22 e) is inserted into the umbrella attaching hole 21 c (umbrella attaching hole 22 c) covers the channel holes 21 d (channel holes 22 d) during normal conditions. When pressure greater than a predetermined value is applied to the umbrella portion 21 g (umbrella portion 22 g) from the channel hole 21 d (channel hole 22 d), the umbrella portion 21 g (umbrella portion 22 g) is elastically deformed to open the channel holes 21 d (channel holes 22 d). The adhesion portion 21 b of the suction-side umbrella unit 21U is adhered to the valve retainer concave portion 24Hb. Conversely, the adhesion portion 22 b of the discharge-side umbrella unit 22U is adhered to the valve retainer concave portion 25Db. The suction-side umbrella unit 21U allows a flow from the suction port 31 toward the pump chamber forming concave channel portion 20 a (pump chamber 23) and does not allow a reverse flow. The discharge-side umbrella unit 22U allows a flow from the pump chamber forming concave portion 20 a (pump chamber 23) toward the discharge port 32 and does not allow a reverse flow. The unit plates 21 a and 22 a of the umbrella units 21U and 22U of the suction side and the discharge side may be formed of one substrate.

An additional cover is not needed for the aforementioned lower housing 20. In the lower housing 20, the closed suction-side channel 24H is formed between the suction port 31 and the pump chamber forming concave portion 20 a, and the closed discharge-side channel 25D is formed between the discharge port 32 and the pump chamber forming concave portion 20 a. In the lower housing 20, a seal ring groove 20 b is also formed at the circumference of the pump chamber forming concave portion 20 a. The seal ring groove 20 b has a deformed D shape that includes a large circular portion 20 b 1 that exceeds a semicircle and a linear portion 20 b 2 that connects the both ends of the large circular portion 20 b 1.

The suction-side umbrella unit 21U and the discharge-side umbrella unit 22U, which is, for example, the valve retainer concave portions 24Hb and 25Db (umbrella portions 21 g and 22 g) are slanted with respect to the plane of the piezoelectric oscillator 30 (non-parallel). Considering a plane that is perpendicular to the piezoelectric oscillator 30 and contains an axis line of the suction port 31 (discharge port 32), in the plane, the aforementioned slant direction is a direction in which the valve retainer concave portions 24Hb and 25Db and the piezoelectric oscillator 30 become more distant in the rear direction of the suction port 31 (discharge port 32) and become closer in the front direction of the suction port 31 (discharge port 32) to each other. As described above, when the suction-side umbrella unit 21U and the discharge-side umbrella unit 22U are slanted with respect to the piezoelectric oscillator 30, the slim lower housing 20 can be achieved without reducing the cross sections of the channels of the suction port 31 and the discharge port 32.

As shown in FIG. 4, the surface (unit plate 21 a of the suction-side umbrella unit 21U (umbrella portion 21 g)) of the valve retainer concave portion 24Hb is not in parallel with the plane of the piezoelectric oscillator 30 and is slanted by an angle of α with respect to the plane of the piezoelectric oscillator 30 in a free state. For example, the channel at the suction-side check valve 21 is not perpendicular to the piezoelectric oscillator 30. On The axis line of the suction port 31 (suction-side channel 24H) is in parallel with the plane of the piezoelectric oscillator 30. The direction of the angle of α is a direction in which the unit plate 21 a (umbrella portion 21 g) of the suction-side umbrella unit 21U becomes spaced apart from the piezoelectric oscillator 30 in the rear direction of the suction port 31 (suction-side channel 24H) and becomes closer to the piezoelectric oscillator 30 in the front direction of the suction port 31 (suction-side channel 24H).

As shown in FIG. 5, the surface (unit plate 22 a of the discharge-side umbrella unit 22U (umbrella portion 22 g)) of the valve retainer concave portion 25Db is not in parallel with the plane of the piezoelectric oscillator 30 and is slanted by an angle of α with respect to the plane of the piezoelectric oscillator 30 in a free state. For example, the channel at the discharge-side check valve 22 is not perpendicular to the piezoelectric oscillator 30. The axis line of the discharge port 32 (discharge-side channel 25D) is parallel with the plane of the piezoelectric oscillator 30. The direction of the angle of α is a direction in which the unit plate 22 a (umbrella portion 22 g) of the discharge-side umbrella unit 22U becomes apart from the piezoelectric oscillator 30 in the rear direction of the discharge port 32 and becomes closer to the piezoelectric oscillator 30 in the front direction of the discharge port 32 (discharge-side channel 25D).

FIGS. 12 and 13 illustrate different preferred embodiments. According to the embodiments illustrated in FIGS. 4 and 5, the axis lines of the suction port 31 (suction-side channel 24H) and the discharge port 32 (discharge-side channel 25D) are parallel with the plane of the piezoelectric oscillator 30, however, according to the preferred embodiment shown in FIGS. 12 and 13, the axis lines of the suction port 31 (suction-side channel 24H) and the discharge port 32 (discharge-side channel 25D) are not in parallel with the plane of the piezoelectric oscillator 30. For example, in a plane that is perpendicular to the diaphragm 30 and contains the axis line of the suction port 31 (suction-side channel 24H), the axis line of the suction port 31 is slanted by an angle of β with respect to the surface of the diaphragm 30. The angle of β is smaller than the angle of α. In a plane that is perpendicular the diaphragm 30 and contains the axis line of the discharge port 32 (discharge-side channel 25D), the axis line of the discharge port 32 is slanted by an angle of β with respect to the surface of the diaphragm 30. The angle of β is smaller than the angle of α.

According to the embodiments illustrated in FIGS. 4, 5, 12, and 13, the lower housing 20 can be achieved without reducing the cross sections of the channels of the suction and discharge ports 31 and 32.

In the lower housing 20, bifurcated channels 24Hd and 25Dd that are bifurcated from the suction-side channel 24H and the discharge-side channel 25D, respectively, are formed to be opened to the pump chamber plate 40 side. In the pump chamber plate 40, communication holes 41 and 42 communicate with the bifurcated channels 24Hd and 25Dd. An interplate suction-side channel 14H that communicates with the communication hole 41 and an interplate discharge-side channel 15D connected to the communication hole 42 are disposed between the upper housing 10 and the pump chamber plate 40. For example, in the pump chamber plate 40, convex portions 41 a and 42 a that are fit into the bifurcated channels 24Hd and 25Dd are formed. The communication holes 41 and 42 are disposed at the center of the convex portions 41 a and 42 a. The reference numerals 41 b and 42 b indicate o-rings for sealing the bifurcated channels 24Hd and 25Dd with the convex portions 41 a and 42 a (communication holes 41 and 42).

In the pump chamber plate 40, the pump chamber comprises a concave portion 40 a (FIGS. 2, 4, and 5) faces the piezoelectric oscillator 30. The suction-side umbrella 11 corresponds to the suction-side umbrella unit 21U and the discharge-side umbrella 12 that corresponds to the discharge-side umbrella unit 22U are attached to the approximate center of the pump chamber forming concave portion 40 a. The suction-side umbrella 11 and the discharge-side umbrella 12 are not shown in FIG. 2. For example, on the pump chamber plate 40, umbrella attaching holes 11 a and 12 a are disposed under the suction-side umbrella unit 21U and the discharge-side umbrella unit 22U. A plurality of channel holes 11 b and 12 b are formed on the circumferences of the umbrella attaching holes 11 a and 12 a. The suction-side and discharge-side umbrellas 11 and 12 include a central axis 11 c (central axis 12 c) inserted into the umbrella attaching hole 11 a (umbrella attaching hole 12 a) and an umbrella portion 11 d (umbrella portion 12 d) covers the channel holes 11 b (channel holes 12 b) during normal operation. When pressure greater than a predetermined value is applied to the umbrella portion 11 d (umbrella portion 12 d) from the channel hole 11 b (channel hole 12 b) side, the umbrella portion 11 d (umbrella portion 12 d) is elastically deformed to open the channel holes 11 b (channel holes 12 b). The suction-side umbrella 11 allows a flow from the upper housing 10 side toward the pump chamber forming concave portion 40 a (pump chamber 13) and does not allow a reverse flow. The discharge-side umbrella 12 allows a flow from the pump chamber forming concave portion 40 a (pump chamber 13) toward the upper housing 10 side and does not allow a reverse flow.

The upper housing 10 has the same shape as the lower housing 20 so that the upper housing 10 overlaps the lower housing 20. In the upper housing 10, a concave portion 14Ha for forms the interplate suction-side channel 14H that communicates with the communication hole 41 with the suction-side umbrella 11 and a concave portion 15Da for forming the interplate discharge-side channel 15D that communicates with the communication hole 42 with the discharge-side umbrella 12 are formed between the upper housing 10 and the pump chamber plate 40 (refer to FIGS. 2 and 4 to 6). The seal ring grooves 14Hc and 15Dc for inserting oval o-rings (seal rings) 14Hb and 15Db are formed at the circumference of the concave portions 14Ha and 15Da. A concave portion 10 a (FIGS. 2 and 6) that inserts the pump chamber plate 40 into the upper housing 10 are formed in the upper housing 10.

A fitting hole 10 c and a positioning protrusion 40 c (FIG. 1) that fits into the fitting hole 10 c while the oval o-rings 14Hb and 15Db are inserted into the concave portions 14Ha and 15Da are formed in the pump chamber plate 40 and the upper housing 10. The positioning protrusion 40 c is fitted into the fitting hole 10 c and adhered to the fitting hole 10 c to form the sealed interplate suction-side channel 14H from the communication hole 41 toward the suction-side umbrella 11 and the sealed interplate discharge-side channel 15D from the communication hole 42 toward the discharge-side umbrella 12. For example, the upper housing 10 and the pump chamber plate 40 are previously integrated with each other by inserting the pump chamber plate 40 into the concave portion 10 a to form the interplate suction-side channel 14H and the interplate discharge-side channel 15D which are closed therebetween. An additional cover for the upper housing 10 and the pump chamber plate 40 is not needed for forming the interplate suction-side channel 14H and the interplate discharge-side channel 15D.

As shown in FIG. 7, in the pump chamber plate 40, a seal ring groove 40 b (that is the same shape as the seal ring groove of the lower housing 20 on the plane) that corresponds to the seal ring groove of the lower housing 20 is formed at the circumference of the pump chamber forming concave portion 40 a that faces the piezoelectric oscillator 30. The seal ring groove 40 b has a deformed D shape that includes a large circular portion 40 b 1 that exceeds a semicircle and a linear portion 40 b 2 that connects the both ends of the large circular portion 40 b 1.

The piezoelectric oscillator 30 may be, for example, a unimorph or bimorph type. FIGS. 8 to 10 are pattern diagrams of an embodiment of the bimorph type piezoelectric oscillator disclosed in Japanese Unexamined Patent Application Publication No. 2005-201235. According to a preferred embodiment, the bimorph type piezoelectric oscillator includes a circular shim 111 at the center and piezoelectric members 112 formed over and under the shim 111 by deposition. The shim 111 includes a conductive metal sheet, for example, a stainless steel sheet having a thickness of about 0.2 mm.

The piezoelectric member 112 is made of Lead Zirconate Titanate (PZT, Pb(Zr, Ti) O₃). The piezoelectric member 112 is polarized in the front-to-back direction of the piezoelectric members 112. The polarization directions of the pair of piezoelectric members located over the front and back surfaces of the shim 111 are the same. As shown in FIG. 8, when the polarization direction of the pair of piezoelectric members 112 is represented by the arrow a or b, the piezoelectric members 112 are polarized in the same direction, which is the thickness direction of the shim 111. For example, a pair of the piezoelectric members 112 that are in contact with the front and back surfaces of the shim 111 are polarized to have different poles from each other, at exposed surfaces thereof. The exposed surfaces of the pair of the piezoelectric members 112 are polarized to have different poles from each other.

When the piezoelectric members 112 are polarized in the same direction, the displacement of the shim 111 can be increased when positive and negative voltages are alternately applied between the shim 111 and the surfaces of the pair of the piezoelectric members 112 which faces the shim 111.

The surfaces of the pair of the piezoelectric members 112 that face the shim 111 are attached to the shim 111 so as to be electrically conductive to the shim 111. Film shaped electrodes 113 are formed on the surfaces which do not face the shim 111. The film shaped electrodes 113 are formed by printing (screen baking) a conducting paste (silver paste or gold paste).

A supply terminal 180 includes a pair of contacts 1811, a connection edge 1812 that connects the contacts 1811 with each other, and a wiring connection portion 1813. The pair of contacts 1811 and the connection edge 1812 constitute a U-shaped cross section. The pair of contacts 1811 have a wider width at the wiring connection portion 1813 and have a gradually narrower width toward the center of the piezoelectric oscillator 30 to form the same approximate triangular shapes. For example, the contact 1811 has the narrowest width at the soldering portion 1131 and has a wider width toward the outside of the piezoelectric oscillator 30.

A wiring connection protrusion 114 that is protruded in the diameter direction of the shim 111 of the piezoelectric oscillator 30 is extended between the pair of contacts 1181. In the wiring connection protrusion 114, a concave portion 1141 for insulation that secures a gap between the wiring connection protrusion 114 and the connection edge that connects the pair of contacts 1181 with the wiring connection protrusion 114 is formed.

Annular spacer insulation rings 115 are located over and under the circular shim 111. Strip insulation sheets 1151 are extended from the pair of spacer insulation rings 115 between the pair of contacts 1181 and the wiring connection protrusion 114 to prevent a short circuit between the shim 111 and the supply terminal 180. The strip insulation sheets 1151 prevent the connection edge 1812 of the supply terminal 180 from moving to the concave portion 1141 of the shim 111 for insulation to secure insulation.

A pair of lead wire holding concave portions 1143 and 1144 are symmetrically formed in the both sides of the wiring connection protrusion 114 in the width direction and are located at the outer side of the piezoelectric oscillator 30 as compared with the concave portion 1141 for insulation. A through hole 1145 for soldering is formed at the inner side of the piezoelectric oscillator 30 as compared with one lead wire holding concave portion 1143.

A through hole 1814 for soldering is formed in correspondence with the through hole 1145 for soldering of the wiring connection protrusion 114 in the wiring connection portion 1813 of the supply terminal 180. The locations of the through holes 1145 and 1814 for soldering are different on the plane, and the lead wires 211 and 221 are soldered into the through holes 1145 and 1814 for soldering. The through holes 1145 and 1814 for soldering are located at different locations on the plane to enable the slim sized diaphragm pump. The lead wires 211 and 221 are held by the lead wire holding concave portions 1143 and 1144 to increase coming-out stopping resistances of the lead wires 211 and 221.

A PPS film (insulation film) 241 (FIG. 8) is adhered to the plane of the piezoelectric oscillator 30. The PPS film 241 includes a piece 241 a in the diameter direction that is extended over the supply terminal 180 to prevent separation between the contacts 1811 and the film shaped electrodes 113 of the piezoelectric oscillator 30.

The shim 111 and the film shaped electrode 113 can be securely wired without disturbing the movement of the piezoelectric oscillator 30 by using the aforementioned connection protrusion 114 of the shim 111 and the wiring structures around the supply terminal 180.

The aforementioned circular piezoelectric oscillator 30 is attached between the pump chamber forming concave portion 20 a of the lower housing 20 and the pump chamber forming concave portion 40 a of the pump chamber plate 40, and the surroundings are sealed by the seal rings 16 and 26 to form the pump chambers 13 and 23. The seal rings 16 and 26 have the same shape as the seal ring groove 20 b of the lower housing 20 and the seal ring groove 40 b of the pump chamber plate 40 and include a large circular portion 16 a (large circular portion 26 a) and a linear portion 16 b (linear portion 26 b). In addition, the supply terminal 180 of the piezoelectric oscillator 30 is located outside of the seal rings 16 and 26, and more specifically, outside of the linear portion 16 b (linear portion 26 b). According to the aforementioned layout, the supply terminal 180 for the piezoelectric members 112 of the piezoelectric oscillator 30 need not to cross over the seal rings 16 and 26, and the seal rings 16 and 26 are not deformed, which in turn improves the durability of the piezoelectric oscillator 30.

The lower housing 20 and the upper housing 10 previously integrated into the pump chamber plate 40 are combined by a fastener (for example, bolts and nuts) to form one body while the piezoelectric oscillator 30 is attached therebetween. An additional adhesive may be used.

In the aforementioned diaphragm pump, when an alternating electric field is applied between the supply terminal 180 of the piezoelectric oscillator 30 and the shim 111 (wiring connection protrusion 114) to elastically deform (oscillate) the piezoelectric oscillator 30 in forward and backward directions, a volume of one pump chamber 13 or 23 increases and a volume of the other pump chamber 23 or 13 decreases. In a stroke for increasing the volume of the pump chamber 13, since the suction-side umbrella 11 opens to introduce a fluid into the pump chamber 13 from the pump port 31 and the volume of the pump chamber 23 simultaneously decreases, a fluid in the pump chamber 23 opens the discharge-side umbrella (unit) 22 to discharge the fluid to the discharge port 32.

In a stroke for decreasing the volume of the pump chamber 13, since the suction-side umbrella (unit) 21 opens to introduce a fluid into the pump chamber 23 from the suction port 31 and the volume of the pump chamber 13 decreases, a fluid in the pump chamber 13 opens the discharge-side umbrella 12 to discharge the fluid to the discharge port 32. Accordingly, it is possible that the pulsation period at the discharge port 32 is reduced to a half of a pulsation period of the diaphragm pump in which the pump chamber is formed on only one side of the piezoelectric oscillator 30. FIG. 11 is a skeletal diagram showing channels of the aforementioned four-valve diaphragm pump.

The preferred embodiments relate to a relation between the umbrellas 21 and 22 provided in the lower housing 20 and the suction and discharge ports 31 and 32. The upper housing 10, the piezoelectric oscillator 30, the pump chamber plate 40, the seal ring 16 or 26, or so is only an example. In addition, the present invention is also applicable to a two-valve type diaphragm pump, for example, a diaphragm pump in which the pump chamber is formed not on the piezoelectric oscillator 30 but under the piezoelectric oscillator 30 (umbrellas 11 and 12 are not formed). The umbrella is used as an example of the check valve, and alternatively, it is possible to use another check valve besides the umbrella. The piezoelectric oscillator is used as the diaphragm in the aforementioned embodiment, and however, it is possible to use an electrostriction oscillator instead of the piezoelectric oscillator. 

1. A diaphragm pump comprising: a housing that comprises a concave portion, a suction port and a discharge port; a diaphragm; a first and second pump chamber; and a suction-side check valve and a discharge-side check valve, wherein the suction-side and discharge-side check valves are more distant from the diaphragm in the inner end side of the suction and discharge ports and are closer to the diaphragm in the outer end side of the suction and discharge ports.
 2. The diaphragm pump according to claim 1, wherein the axis lines of the suction and discharge ports are extended in parallel with an extending plane of the diaphragm.
 3. The diaphragm pump according to claim 1, wherein the axis lines of the suction and discharge ports are not parallel with the extending plane of the diaphragm and is slanted with respect to the extending plane of the diaphragm so that an angle between the axis lines of the suction and discharge ports and the extending plane of the diaphragm is smaller than an angle between the extending plane of the diaphragm and a plane where the suction-side and discharge-side check valves are provided.
 4. The diaphragm pump according to claim 1, wherein the suction-side and discharge-side check valves are formed as suction-side and discharge-side check valve units that are separate from the housing, and the suction-side and discharge-side check valve units are attached to pump chamber-side opening ends of the suction and discharge ports.
 5. The diaphragm pump according to claim 4, wherein the suction-side and discharge-side check valve units are provided on the same substrate.
 6. The diaphragm pump according to claim 1, wherein the check valves have an umbrella shape.
 7. The diaphragm pump according to claim 1, wherein the diaphragm is a piezoelectric oscillator.
 8. The diaphragm pump according to claim 1, wherein the diaphragm obturates the concave portion.
 9. The diaphragm pump according to claim 1, the pump chambers are partitioned by the concave portion and an oscillating diaphragm.
 10. The diaphragm pump according to claim 1, wherein the suction port and the discharge port are formed in a direction along a plane of the diaphragm and of which inner ends communicate with the pump chamber.
 11. The diaphragm pump according to claim 1, wherein the suction-side check valve is provided between the inner end of the suction port and the pump chamber, and a discharge-side check valve is provided between the inner end of the discharge port and the pump chamber.
 12. The diaphragm pump according to claim 1, wherein the suction-side and discharge-side check valves are slanted with respect to a plane which is perpendicular to the diaphragm and contains an axis line of the suction port and a plane which is perpendicular to the diaphragm and contains an axis line of the discharge port.
 13. The diaphragm pump according to claim 1, wherein the diaphragm is an electrostriction oscillator. 